The attendance for a rugby match is 8400 people to the nearest 100.
Write down the minimum possible attendance.
How to approach this question
The number is rounded to the nearest 100. First, find the range of values that would round to 8400. The degree of accuracy is 100. Halve this to get 50. The lower bound is 8400 - 50 and the upper bound is 8400 + 50. The question asks for the minimum possible attendance, which is the lower bound.
Full Answer
To find the lower bound (minimum), you take the degree of accuracy (100), halve it (50), and subtract it from the rounded number.
8400 - 50 = 8350.
The minimum possible attendance is 8350.
When a number is rounded to the nearest 100, it means the actual value is closer to that multiple of 100 than to any other. The "error interval" is found by taking the degree of accuracy (100), halving it (50), and then adding and subtracting this from the rounded value.
Lower Bound = 8400 - 50 = 8350.
Upper Bound = 8400 + 50 = 8450.
This means the actual attendance `A` is in the interval 8350 ≤ A < 8450. The minimum possible attendance is the lower bound, which is 8350.
Common mistakes
✗ Calculating the upper bound instead of the lower bound.
✗ Using half of 10 instead of half of 100 (e.g., 8400 - 5 = 8395).
✗ Stating the lower bound of the error interval incorrectly as 8349 or 8349.5.
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